Sept. 1,1924 Bacterial Pustule of Soybean 247 
Type of colony in relation to , 
virulence. —Typical infections have 
been obtained with all the types of 
colonies described. Apparently there 
is no relation between the colony 
markings and the degree of virulence. 
COLONIES OF BACTERIUM PHASEOLI EFS. 
ON 1 PER CENT BEEF AGAR PLATES 
AT ROOM TEMPERATURE (PL. 7). 
The type of colony most commonly 
appearing in isolation plates of Bad. 
phaseoli EFS.is round,smooth, wet-shin¬ 
ing, slightly con vex with thin,clear, color¬ 
less regular margins (PI. 7, D). Fre¬ 
quently, however, colonies with coarse 
or fine concentric striae are present 
(PI. 7, A, J) and more rarely colonies 
with distinct radiating lines (PI. 7, 
B, C); as in the case of the soybean 
organism, these markings are internal. 
Occasionally there is a lobed and fluted 
colony (PI. 7, I), and there are still 
other types now and then (PI. 7, K to 
M). In colony 7, May 9, 1919 (Pi. 7, 
L), the center was considerably de¬ 
pressed, as was that of most of the 
colonies on the same plate. Only 
twice have the colonies with internal 
convolutions so characteristic of Bact. 
phaseoli sojense been observed (PI. 7, C). 
As in the case of Bact. phaseoli so¬ 
jense, the different types of colonies 
sometimes appeared on the same plate 
(PI. 7, A, B). All colonies in Plate 7 
produced infection except K and M, 
which were not tested. One set of 
comparative inoculations is illustrated 
in Plate 7, E to H. On August 12, 
1918, Lima bean pods were sprayed 
with water and smeared with slime 
from potato cultures of August 3 
of four types of colonies—striated, 
with radiating lines, convoluted, and 
unmarked (PI: 7 ,A to D). The pods 
were then wrapped in oiled paper. 
When the paper was removed, August 
19, there were water-soaked spots (PI. 
4, G), and on August 31, 19 days after 
inoculation, the pods were badly in¬ 
fected, as shown in Plate 7, E to H. 
In this experiment the striated and un¬ 
marked colonies were by far the most 
infectious, but in other inoculations 
the type with radiating lines has also 
been very virulent. The convoluted 
type came from a much older isolation 
than-the others. It was isolated in 
Idaho in 1914, and the others in 1917. 
This may explain its lesser degree of 
virulence, since it was formerly very 
infectious. 
MORPHOLOGY OF BACTERIUM 
PHASEOLI SOJENSE 
Short rods with rounded ends, single 
or in pairs 1.4 to 2.3 u X 0.5 to 0.9 n. 
Actively motile, 1-2 polar flagella. 
Rods from water suspension of beef 
agar slants 1 to 3 days old stained with 
Casares-Gil’s (PI. 3, E) and van Er- 
mengem’s flagella stains. Smith de¬ 
scribes Bact. phaseoli EFS. as one- 
flagellate (16). 
LONGEVITY 
In cultures. — Bacterium, phaseoli 
sojense lives on potato at room tem¬ 
perature three to five months provided 
inoculation is made on freshly made 
cylinders. Stock cultures in the ice 
box have been alive one year and four 
months on both potato and beef agar 
(stabs) in small-bore tubes ( 13 ^ cm. 
diameter). On the other hand, beef 
agar stock cultures in tubes 2 cm. in 
diameter did not live six months in the 
ice box. Bact. phaseoli EFS. has lived 
1K years on beef agar (small-bore 
tubes) in the ice box but has died in 
three months in the ice box when 
growing in beef agar in the large-bore 
tubes. 
In the plant. — Bact. phaseoli sojense 
has been plated from soybean leaves 
kept dry in the laboratory for eight 
months, and colonies so obtained -were 
very infectious. Very few of the organ¬ 
isms were alive, however, and it is 
often difficult or impossible to isolate 
the parasite from such material. 
RETENTION OF VIRULENCE 
Bacterium phaseoli sojense does not 
lose its virulence readily. Excellent 
infections have been obtained with a 
colony 13^2 years after its isolation. 
A colony of Bad. phaseoli EFS. pro¬ 
duced infection on Lima bean pods 3 
years 113 ^ months after its isolation. 
It was not, however, as virulent as 
colonies from more recent isolations. 
EXPLANATORY LEGEND FOR PLATE 6 
Bacterium phaseoli sojense. (Photographs by James F. Brewer) 
Colony types on beef agar plates, all pathogenic. X10. All markings are internal, surface smooth. 
A.—From Lima bean pod (PI. 4, E), convoluted colony 6 days old. 
B—From pustule on soybean (PI. 1, E), colony with radiating lines; colony 3 weeks old. 
C.—From pale green spots with red centers on soybean; convoluted colony 9 days old. 
D and E—On same isolation plate, from soybean: E, concentric striae; colonics 7 days old. 
F. —From bush string bean (PI. 4, A); colony 8 days old. 
G. —From yellowish-green spot on dwarf wax bean; colony 5 days old. 
